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Poly(ethylene glycol)-based Polymers: Synthesis, Characterization, and Application

Dilla, Rodger Alan
http://rave.ohiolink.edu/etdc/view?acc_num=akron1555344606484453

Abstract Details

2019, Doctor of Philosophy, University of Akron, Polymer Science.
PEG and PEG-based hydrogels offer many advantages for tissue engineering scaffolds as a consequence of their hydrophilicity, wide range of cross-linking chemistries, low immunogenicity, and tunable mechanical properties. Human mesenchymal stem cells (hMSCs) have demonstrated varying lineage commitment in response to the mechanical and degradation properties of PEG hydrogels within which they were encapsulated. Furthermore, the proliferation and differentiation of pre-osteoblasts have been shown to be influenced by cell scaffold features such as porosity and surface area. Therefore, there is a need to develop materials that provide precise control over mechanical properties and final scaffold morphology to allow for the accurate assessment of material properties on cell behavior. Few hydrogel systems can alter mechanical moduli without changing design elements such as composition, concentration, and stoichiometry. By employing the pH-sensitive kinetics of oxime bond formation, PEG-oxime hydrogels with a shear modulus range of G’ = 5-25 kPa were created from solutions of identical precursor composition, concentration, and stoichiometry simply by varying the pH and buffer concentration of the gelation solution. Equilibrium gel swelling and small angle neutron scattering (SANS) experiments indicated fundamental differences in bond connectivity (i.e. increased loops and dangling ends) were responsible for the observed range in G’. Finally, a 24 h cell viability assay was performed to demonstrate the cell viability of these materials. This study provided important insight in isolating material properties from the chemistry of cross-linking and will inspire further investigations into the effects of material properties on cell behavior. Hydrogel processing is often limited to molding techniques, preventing the formation of complex scaffold morphologies. By utilizing linear PEG as a macro-initiator for the ring opening polymerization of poly(propylene fumarate) (PPF), diblock and triblock copolymer species were synthesized in a series of varying PEG and PPF block lengths which can be photo-crosslinked by the double bonds in PPF. Hydrogels printed by continuous digital light processing (cDLP) additive manufacturing demonstrated a 10-fold increase in extension at break while maintaining the same elastic modulus as those printed from traditional diethyl fumarate (DEF) solutions. High cell viability (> 90%) of three different cell types (nerve, endothelial, and bone) was shown for all PEGPPF hydrogels, demonstrating wide application potential. This system thereby provides handles to tune and investigate both material properties and macroscopic scaffold architecture effects on cell behavior. Finally, the self-assembly of PEGPPF diblock and triblock copolymers were explored as a function of changing solvent identity, initial polymer concentration, and rate of water addition. Resulting particle sizes were observed with Rh ~15-100 nm by DLS and cryo-TEM measurements, and the critical aggregation concentration was estimated by a Nile Red fluorescence assay (~0.14 mg•mL-1 for diblocks, ~0.36 mg•mL-1 for triblocks). Core cross-linking with a photoinitiator was demonstrated, indicating this copolymer system can be utilized to produce robust, stable nanoparticles.
Matthew Becker, PhD (Advisor)
Andrey Dobrynin, PhD (Committee Chair)
Yu Zhu, PhD (Committee Member)
Coleen Pugh, PhD (Committee Member)
Bryan Vogt, PhD (Committee Member)
147 p.
Biomedical Research; Organic Chemistry; Polymer Chemistry; Polymers
PEG; hydrogel; tunable modulus; tissue engineering; additive manufacturing; self assembly

Recommended Citations

Citations

  • Dilla, R. A. (2019). Poly(ethylene glycol)-based Polymers: Synthesis, Characterization, and Application [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1555344606484453

    APA Style (7th edition)

  • Dilla, Rodger. Poly(ethylene glycol)-based Polymers: Synthesis, Characterization, and Application. 2019. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1555344606484453.

    MLA Style (8th edition)

  • Dilla, Rodger. "Poly(ethylene glycol)-based Polymers: Synthesis, Characterization, and Application." Doctoral dissertation, University of Akron, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1555344606484453

    Chicago Manual of Style (17th edition)

akron1555344606484453
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© 2019, all rights reserved.
This open access ETD is published by University of Akron and OhioLINK.